This application claims the benefit of Japanese Application No. 2000-338033 filed in Japan on Nov. 6, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an illumination device, or more particularly, an illumination device for radiating illumination light (flashlight) to an object during photography performed by a camera.
2. Description of the Related Art
Conventionally, when a camera is used to perform photography, if the photography is performed at night, indoors, or with an object backlit, an illumination device is used to radiate illumination light (flashlight) to the object.
The illumination device is mounted in a part of a camera body so that illumination light (flashlight) can be radiated to an object while being interlocked with a photographic action of the camera. Photography is thus achieved.
FIG. 22 and FIG. 23 show sectional views of a conventional illumination device. An illustrated illumination device 10 has a cylindrical flash tube 12, for example, a xenon (Xe) flash tube placed inside the back 11a of a reflector 11 having a radial section. At this time, the flash tube 12 is placed so that the longitudinal direction thereof will be orthogonal to a center axis 13 of the reflector 11. All that restricts the direction of light emanating from a glowing member of the flash tube 12 is the reflector 11 including the back 11a thereof. Light emanating from the glowing member of the flash tube 12 is not reflected from the inner wall of the reflector 11 but radiated directly to the outside of the reflector 11. Besides, the light is reflected from the inner wall of the reflector 11 and radiated to the outside of the reflector 11. Besides, the light is reflected from inner wall of the reflector 11 and radiated to the outside of the reflector 11. Other part of the light (indicated with a mark x) leaks out through a gap between the reflector 11 and flash tube 12.
FIG. 22 shows numerous light rays emitted at different angles from a center point O in the glowing member of the flash tube 12. FIG. 23 shows numerous light rays emitted at different angles from a glowing point A that is off the center point O in the glowing member of the flash tube 12. Part of the light rays are emitted from the glowing points and radiated directly to outside through the interior of the reflector 11. Other part of the light rays are reflected from the inner surface of the reflector 11 and radiated to outside. Moreover, still other part of the light rays is directed from the glowing points to the back 11a of the reflector. The light rays directed from the glowing points to the back 11a of the reflector fall into three parts. That is to say, one part of the light rays is reflected from the inner surface of the back 11a of the reflector, propagated through the interior of the reflector 11, and emitted through an opening 11b. Other part of the light rays is reflected from the inner surface of the reflector 11 and then radiated through the opening 11b. Still other part of the light rays is radiated to outside through the gap between the reflector 11 and flash tube 12 on both sides without being reflected from the inner surface of the reflector 11 (this part of the light rays does not effectively work on an object).
Each angle written in FIG. 22 is an angle of radiation (an angle to the center axis of radiation 13) at which a light ray that passes through the reflector 11 is radiated to an object (upwards in the drawing), which is not shown, through the opening 11b that opens radially. An angle of radiation required to distribute light to a relatively narrow area and comparable to an angle of view offered by a photography lens employed shall be, for example, 16xc2x0. Light rays indicated with angles that are larger than 16xc2x0 are radiated to an area outside a desired photographic range in which an object lies. The light rays do not work effectively on the object during photography. The conventional illumination device shown in FIG. 22 and FIG. 23 has numerous light rays radiated at angles of radiation that exceed an effective range from 0xc2x0 to 16xc2x0, and thus suffers from poor radiation efficiency.
Accordingly, proposals have been made in efforts to improve the radiation efficiency or radiation characteristic of an illumination device.
For example, Japanese Unexamined Patent Application Publication No. 4-138440 describes the structure of an illumination device that radiates light, which diverges from a cylindrically long discharge tube, forwards. Specifically, prisms are placed in front of both the sides of the discharge tube so that light traveling in the longitudinal direction of the discharge tube will be converged forwards.
Moreover, Japanese Unexamined Patent Application Publication No. 10-115853 describes a structure having a plurality of prisms that acts like a light guide located in front of a glowing member, otherwise, one prism is slit in order to draw out the similar effect as that provided by a plurality of light guides.
On the other hand, an illumination device for cameras is required to have an angle of radiation comparable to an angle of view offered by a photography lens employed in a camera (a wide-angle lens, a standard lens, a telephoto lens, etc.).
However, in the structure described in the Japanese Unexamined Patent Application Publication No. 4-138440, only prisms are placed in front of both the sides of a discharge tube. As FIG. 1A in the above publication illustrates, light that is emitted from the glowing member of the discharge tube and radiated forwards without being passed through any prism travels rectilinearly but is neither refracted nor reflected in a space between the prisms placed on both the sides of the discharge tube. Therefore, a radiation range of the light is wide. If light must be distributed to a small area, the light cannot be converged efficiently. Moreover, the distance between the prisms placed on both the sides of the discharge tube must be set longer than an arc length of a discharge tube. When a large-energy flash tube characterized by an arc length larger than an arc length made by a discharge tube is used to distribute light to a small area, radiation efficiency is very poor.
Furthermore, the above publication discloses a type of flash tube having a reflecting member placed inside the prisms as illustrated in FIG. 3A of the above publication. This type of flash tube has a drawback that the reflecting surface of the reflecting member must be in a complex shape. Besides, even when light must be distributed to a narrow area, the light cannot be converged efficiently.
According to the Japanese Unexamined Patent Application Publication No. 10-115853, a light guide unit is included independently of a housing panel member of a camera body located in front of the light guide unit. This means that a housing panel member must be procured independently of a light guide member. Moreover, light is radiated by merely utilizing total reflection caused by light guides. Light is therefore radiated radially from the emitting surfaces of the light guides opposed to the incidence surfaces thereof. This poses a problem in that light is hard to be efficiently converged on a narrow area.
Accordingly, an object of the present invention is to provide an illumination device that is required to distribute light to a relatively narrow area and can allow light to efficiently converge on an object.
According to a first aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a light source, forwards. The illumination device consists mainly of a prism and a reflecting member.
The prism has an incidence surface and a transmitting/totally-reflecting surface. The incidence surface is opposed to the light source so that light emanating from the light source can fall on the incidence surface. The transmitting/totally-reflecting surface can transmit or totally reflect light, which has passed through the incidence surface, according to an angle of incidence. The transmitting/totally-reflecting surface radiates transmitted light forwards, and directs totally-reflected light laterally.
The reflecting member reflects light, which is totally reflected laterally from the transmitting/totally-reflecting surface, forwards.
According to the first aspect, light emanating from the light source falls on the prism. The light is transmitted or totally reflected from the transmitting/totally-reflecting surface of the prism according to an angle of incidence. The transmitted light is radiated forwards, while the totally-reflected light is directed laterally. The reflecting member reflects light, which is totally reflected laterally from the prism, forwards. The combination of the prism and reflecting member efficiently radiates light, which emanates from the light source, to a specific forward area.
According to a second aspect of the present invention, there is provided an illumination device consisting mainly of a flash tube and a prism.
The flash tube is cylindrically long and emits illumination light.
The prism is located in front of the flash tube and has a transmitting/totally-reflecting surface that transmits or totally reflects light, which diverges from the flash tube, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally.
According to the second aspect, the prism having the transmitting/totally-reflecting surface opposed substantially entirely to the longitudinal direction of the flash tube is located in front of the cylindrically long flash tube. Light emanating from the flash tube falls on the prism and is transmitted or totally reflected from the transmitting/totally-reflecting surface of the prism according to an angle of incidence. Light transmitted from the prism is radiated forwards, while light totally-reflected therefrom is directed laterally. Light is thus oriented. Consequently, if the light totally-reflected from the prism and directed laterally is directed forwards using any other means, the light is efficiently converged on a specific forward area.
According to a third aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a cylindrically long flash tube, forwards. The illumination device consists mainly of a first prism and a second prism.
The first prism is located in front of the flash tube, and has a first transmitting/totally-reflecting surface opposed substantially entirely to the longitudinal direction of the flash tube. The first transmitting/totally-reflecting surface transmits light that diverges from the flash tube at an angle smaller than a predetermined angle relative to the center axis of radiation in the illumination device that lies in the longitudinal direction of the flash tube, and radiates the light forwards. Moreover, the first transmitting/totally-reflecting surface totally reflects light that diverges from the flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in the illumination device, and directs the light laterally.
The second prism is located in front of the flash tube and has a second transmitting/totally-reflecting surface opposed substantially entirely to the longitudinal direction of the flash tube. The second transmitting/totally-reflecting surface transmits light that diverges from the flash tube at an angle smaller than the predetermined angle relative to the center axis of radiation in the illumination device that lies in the longitudinal direction of the flash tube, and radiates the light forwards. Moreover, the second transmitting/totally-reflecting surface totally reflects light that diverges from the flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in the illumination device, and directs the light laterally.
According to a fourth aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a cylindrically long flash tube, forwards. The illumination device consists mainly of a prism unit and a reflecting member.
The prism unit is located in front of the flash tube and has an incidence surface, a transmitting/totally-reflecting surface, and an emitting surface. Light diverging from the flash tube falls on the incidence surface. The transmitting/totally-reflecting surface transmits or totally reflects light, which has passed through the incidence surface, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally. The emitting surface finally radiates the light, which is transmitted or totally reflected from the transmitting/totally-reflecting surface, forwards.
The reflecting member reflects light, which is laterally reflected totally from the transmitting/totally-reflecting surface, forwards towards the emitting surface.
According to a fifth aspect of the present invention, there is provided an illumination device consisting mainly of a flash tube and a prism.
The flash tube is cylindrically long and emits illumination light.
The prism is located in front of the flash tube and has a transmitting/totally-reflecting surface. The transmitting/totally-reflecting surface transmits or totally reflects light, which diverges from the flash tube, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube while being inclined by a predetermined slope relative to the longitudinal direction of the flash tube, so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally.
According to a sixth aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a flash tube, forwards. The illumination device consists mainly of an optical prism and a pair of air layers.
The optical prism has a transmitting/totally-reflecting surface that transmits or totally reflect light, which diverges from the flash tube, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the flash tube in front of the flash tube, and used to converge and radiate light forwards.
The pair of air layers is formed in the optical prism in order to constitute the transmitting/totally-reflecting surface so that the air layers will have a substantially uniform width and face the flash tube.
According to the sixth aspect, the optical prism having the transmitting/totally-reflecting surface opposed substantially entirely to the flash tube is located in front of the flash tube. Using the transmitting/totally-reflecting surface, light diverging from the flash tube is converged and radiated forwards. The gaps, that is, the pair of air layers which has a substantially uniform width is formed in the optical prism, thus realizing the transmitting/totally-reflecting surface.
According to a seventh aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a cylindrically long flash tube, forwards. The illumination device consists mainly of an optical prism, a reflecting member, a housing panel, and a pair of air layers.
The optical prism is located in front of the flash tube, and has an incidence surface, a transmitting/totally-reflecting surface, and an emitting surface. Light diverging from the flash tube falls on the incidence surface. The transmitting/totally-reflecting surface transmits or totally reflects light, which has passed through the incidence surface, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube, so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally. The emitting surface finally radiates the light, which is transmitted or totally reflected from the transmitting/totally-reflecting surface, forwards.
The reflecting member is formed to cover at least part of the periphery of the optical prism, and reflects light, which passes the periphery of the optical prism, towards the emitting surface.
A housing panel is formed integratelly with the emitting surface of the optical prism and exposed as a housing member.
The pair of air layers is formed in the optical prism in order to constitute realize the transmitting/totally-reflecting surface so that the air layers will have a substantially uniform width and be opposed to the flash tube.
According to the seventh aspect, light diverging from the cylindrically long flash tube falls on the optical prism, and is transmitted or totally reflected from the transmitting/totally-reflecting surface according to an angle of incidence. Transmitted light is radiated forwards, and totally-reflected light is directed laterally. The reflecting member directs the light, which is totally reflected laterally from the prism, forwards. Consequently, the combination of the prism and reflecting member efficiently radiates light, which diverges from the flash tube, to a specific forward area. Moreover, the housing panel is formed integratelly with the emitting surface of the optical prism. The housing panel integrated with the optical prism is attached to the housing member of a camera body, whereby the optical prism encased in front of the flash tube in the reflecting member is mounted in the camera body. Thus, the illumination device can be readily positioned and fixed to the camera body.
According to an eighth aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a flash tube, forwards. The illumination device consists mainly of an optical prism and a housing panel.
The optical prism has a transmitting/totally-reflecting surface that transmits or totally reflects light, which diverges from the flash tube, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the face of the flash tube. Using the transmitting/totally-reflecting surface, light is converged and radiated forwards.
The housing panel is formed integratelly with the emitting surface of the optical prism and exposed as a housing member.
According to a ninth aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a cylindrically long flash tube, forwards. The illumination device consists mainly of an optical prism, a housing panel, and a reflecting member.
The optical prism is located in front of the flash tube and has an incidence surface, a transmitting/totally-reflecting surface, and an emitting surface. Light diverging from the flash tube falls on the incidence surface. The transmitting/totally-reflecting surface transmits or totally reflects light, which has passed through the incidence surface, according to an angle of incidence at which the light meets the surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally. The emitting surface finally radiates light, which is transmitted or totally reflected from the transmitting/totally-reflecting surface, forwards.
The housing panel is formed integratelly with the emitting surface of the optical prism and exposed as a housing member.
The reflecting member is formed to cover at least part of the periphery of the optical prism, and reflects light, which passes the periphery of the optical prism, towards the emitting surface.
According to a tenth aspect of the present invention, there is provided an illumination device for radiating diverging light, which emanates from a cylindrically long flash tube, forwards. The illumination device consists mainly of a first prism, a second prism, a reflecting member, a housing prism, and a prism unit forming means.
A first prism is located in front of the flash tube and has a first transmitting/totally-reflecting surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube, so that light diverging from the flash tube at an angle smaller than a predetermined angle relative to the center axis of radiation in the illumination device that lies in the longitudinal direction of the flash tube will be transmitted and radiated forwards, and light diverging from the flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in the illumination device will be totally reflected and directed laterally.
A second prism is located in front of the flash tube and has a second transmitting/totally-reflecting surface. The transmitting/totally-reflecting surface is opposed substantially entirely to the longitudinal direction of the flash tube, so that light diverging from the flash tube at an angle smaller than the predetermined angle relative to the center axis of radiation in the illumination device that lies in the longitudinal direction of the flash tube will be transmitted and radiated forwards, and light diverging from the flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in the illumination device will be totally reflected and directed laterally.
The reflecting member is formed to cover at least part of the periphery of the optical prism and reflects light that passes the periphery of the optical prism.
The housing prism has an incidence surface and an emitting surface. Light transmitted or totally reflected from the transmitting/totally-reflecting surface finally falls on the incidence surface. The emitting surface emits the light, which falls on the incidence surface, forwards. The emitting surface is exposed as a housing member.
The prism unit forming means is used to place the first transmitting/totally-reflecting surface of the first prism and the second transmitting/totally-reflecting surface of the second prism that are opposed to the incidence surface of the housing prism with a gap of a substantially uniform width between them.